Lead frame, method of manufacturing the same, semiconductor device using lead frame and method of manufacturing semiconductor device

ABSTRACT

There is provided a lead frame which comprises: a lead frame body comprising a sheet-shaped body made of metal; a groove portion for forming a lead which is formed by a predetermined depth in a lead forming region on a surface of the lead frame body; and a lead portion formed so that the lead portion can protrude from the groove portion onto the surface of the lead frame body, the lead portion being made of material different from material of the lead frame body. A thin type semiconductor device is provided in which the above lead frame is used and after a chip is mounted, the lead frame body is removed by means of etching.

[0001] The present application is based on Japanese Patent ApplicationNo. 2003-008349, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a lead frame, a method ofmanufacturing the lead frame, a semiconductor device using the leadframe and a method of manufacturing the semiconductor device. Moreparticularly, the present invention relates to the formation of anexternal terminal of a resin sealing type semiconductor device.

[0004] 2. Description of the Related Art

[0005] Recently, electronic equipment such as a personal computer andcellular phone has been downsized. According to this tendency ofdownsizing electronic equipment, electronic parts are highly denselyassembled. Therefore, in the field of a semiconductor device such as adiode and transistor, in order to reduce the assembling area, a faceassembly type semiconductor device is widely used.

[0006] In this face assembly type semiconductor device, in order toreduce the manufacturing cost, concerning the form of a package, a resinsealing type semiconductor device is widely used because the materialcost is low and the productivity is high.

[0007] For the object of reducing the size of a semiconductor device,the following technique is proposed. A lead frame, in which a protrusionis formed in a region that becomes a lead, is used, and a semiconductorchip is mounted on the lead frame and electrically connected. After thecompletion of resin sealing, the lead frame is removed together with theresin by polishing from the reverse side while leaving this protrusionso that the thickness can be reduced, and then dicing is conducted so asto divide it to individual semiconductor devices.

[0008] As an example, the semiconductor device shown in FIGS. 11A to 11Cis proposed. Concerning this semiconductor device, refer to PatentDocument 1. This semiconductor device is formed as follows. Asemiconductor chip is fixed to and electrically connected to a leadframe, and then resin sealing is conducted from the reverse side of thelead frame. Then, the semiconductor chip 72 is fixed onto the leadframe. A frame comprising the islands 61, 61A, which become electrodesused for an external connection, and also comprising a plurality of leadterminals 62, 63, 62A, 63A, which become the other electrodes used foran external connection of the semiconductor chip 72 fixed to theadjoining island, is fixed to the semiconductor chip 72 being attachedwith conductive paste on the islands of the plurality of lead framesarranged in the row direction by the connecting bar and electricallyconnected to the adjoining lead terminal. A resin layer is formed on thelead frame so that the semiconductor chip and the lead terminal can becovered and reverse faces of the island and the lead terminal can beexposed. The islands, to which the semiconductor chips are fixed, andthe semiconductor chips are individually divided into individual piecesin a region surrounding the electrically connected lead terminal.

[0009] [Patent Document 1]

[0010] Unexamined Japanese Patent Publication No. Hei-10-313082

[0011] According to this technique, it is possible to downsize thesemiconductor device. However, on the contact face of the resin sealingtype semiconductor device with the printed board, that is, on thereverse side of the semiconductor integrated circuit device, since theresin face and the lead terminals, which become the external terminals,are on the same plane, even when a small deviation of the size iscaused, it is impossible to positively connect with the circuit patternon the printed board, which could cause an imperfect contact.

[0012] In order to protrude the lead terminals, it is necessary toprovide a plating process in which the bumps (the protruding portions)are formed after the completion of dicing, which increases the man-hourin the manufacturing process.

[0013] The present invention has been accomplished in view of the aboveactual circumstances. It is an object of the present invention toprovide a highly reliable thin type semiconductor device capable ofbeing easily manufactured.

SUMMARY OF THE INVENTION

[0014] The present invention provides a lead frame comprising: a leadframe body comprising a sheet-shaped body made of metal; a grooveportion for forming a lead which is formed by a predetermined depth in alead forming region on a surface of the lead frame body; and a leadportion formed so that the lead portion can protrude from the grooveportion onto the surface of the lead frame body, the lead portion beingmade of material different from material of the lead frame body.

[0015] According to the above constitution, the lead portion is formedprotruding from the groove portion. Therefore, assembling can beconducted in such a manner that the lead portion protrudes from thesealing resin. Therefore, when a semiconductor device is assembled to aprinted board, it is possible to provide the semiconductor device inwhich no imperfect contact is caused. Accordingly, it is possible toform a stable external terminal structure without providing a platingprocess after the completion of resin sealing.

[0016] This external terminal can be formed under the condition that itis electrically connected via the lead frame body. Therefore, when theexternal terminal is formed, it is possible to adopt a means ofelectrolytic plating in which the lead frame body is used as anelectrode. Accordingly, the thickness can be controlled with highaccuracy, and a highly reliable external terminal can be formed withhigh efficiency.

[0017] After the semiconductor chip is mounted on the lead portion, anelectrical connection is conducted by means of wire bonding or directbonding. Then, resin sealing is conducted, and the lead frame body isremoved from the reverse face by means of etching. Due to the foregoing,it becomes possible to provide a highly reliable thin semiconductordevice. To be specific, the thickness of the semiconductor device can bereduced to about three fourths of the thickness of the conventionalsemiconductor device.

[0018] In the case of mounting the semiconductor chip, the lead portionis fixed to the lead frame body. Therefore, no positional shift iscaused, and bonding can be positively performed with high reliability.Further, since the device is positively fixed by means of resin sealingand the lead frame is removed from the reverse face, the semiconductordevice is not deformed.

[0019] Further, after the completion of resin sealing, dicing isconducted so that it can be divided into individual semiconductordevices. In this case, the lead portion can be made not to exist in thedicing region. Accordingly, in the case of dicing, it is not necessaryfor a cutting blade to cut off the lead portion. Accordingly, abrasionof the cutting blade can be reduced and the life of the cutting bladecan be extended.

[0020] Since the lead is guided out only from a principal plane of thesealing resin and not guided out from the side of the sealing resin,there is no possibility that moisture gets into the sealing resin fromthe atmospheric air via the lead guiding portion. Accordingly, thereliability can be enhanced.

[0021] Further, it is possible to freely design the profile of the crosssection of the lead portion according to the profile of the crosssection of the groove portion. Accordingly, a highly dense and accuratelead portion pattern can be easily formed.

[0022] The present invention provides a lead frame, the lead including:a first conductor layer formed in the groove portion; a second conductorlayer formed on the first conductor layer; and a third conductor layerformed on the second conductor layer, wherein the first conductor layeris assembled to an assembling member, and the third conductor layer isassembled to a bonding pad of a semiconductor chip.

[0023] According to the above constitution, it is preferable that thelead comprises a three-layer-structure and made of materialcorresponding to a member to be connected. Further, it is preferablethat the main body located at the center is made of an inexpensiveconductive material.

[0024] The present invention provides a lead frame, in which the firstconductor layer covers the entire inner wall of the groove portion.

[0025] According to the above constitution, a semiconductor device canbe formed with this lead frame in such a manner that the lead portionexposed from the sealing resin comprises only the first conductor layer.Accordingly, when the first conductor layer is made of stable metal suchas gold capable of easily forming an alloy together with solder, astable external terminal structure can be formed without conducting aplating process after the completion of sealing.

[0026] In this case, only the first conductor layer may be made ofstable material which is difficult to be oxidized, and the secondconductor layer may be made of inexpensive metal of low resistance. Thefirst and the third conductor layer may be made of material which can beeasily joined by solder. The third conductor layer may be made of thesame material as the material of the second conductor layer.

[0027] It is preferable that the first conductor layer covers the entireinner wall of the groove portion and also covers a portion of the flatplane in the periphery of the groove portion. Due to the foregoing, itis possible to positively prevent the second conductor layer from beingexposed. Therefore, it is possible to form a highly reliablesemiconductor device.

[0028] In a lead frame of the present invention, an interface of thefirst and the second conductor layer is located above the surface of thelead frame body.

[0029] According to the above constitution, after the completion ofassembling, the second conductor layer is perfectly sealed with thesealing resin, so that the second conductor layer can not be exposed tothe surface. Therefore, in the same manner as that of the above leadframe, a stable lead frame of long life can be provided.

[0030] In a lead frame of the present invention, the lead includes abarrier layer for suppressing a reaction between the lead frame body andthe first conductor layer, the barrier layer being provided between thefirst conductor layer and the groove portion.

[0031] According to the above constitution, since the barrier layer madeof nickel or titanium is existing, an interface reaction is causedbetween the first conductor layer and the lead frame body by heatgenerated in the bonding process, and the first conductor layer can beprevented from deteriorating. This barrier layer may be formed thin.Further, this barrier layer may be finally removed.

[0032] In a lead frame of the present invention, the first conductorlayer is made of metal capable of forming an alloy together with solder.

[0033] According to a semiconductor device to which the above lead frameis assembled, bonding can be appropriately performed when thesemiconductor device is assembled to a printed board.

[0034] In a lead frame of the present invention, the third conductorlayer is made of metal, the wire bonding property of which is high.

[0035] According to the above constitution, when the third conductorlayer is made of metal such as gold, the wire bonding property of whichis high, the semiconductor chip can be easily assembled.

[0036] In a lead frame of the present invention, the third conductorlayer is made of metal having a high bonding property when the metal isbonded to a bonding pad of a semiconductor chip.

[0037] According to the above constitution, even when a semiconductorchip is mounted by means of direct bonding, assembling can be easilyconducted.

[0038] In a lead frame of the present invention, the film thickness ofthe first and the second conductor layer is 0.5 to 2 μm.

[0039] According to the above constitution, the entire thickness can besufficiently decreased. Further, the film thickness of the secondconductor layer can be sufficiently increased. Therefore, it is possibleto compose a semiconductor device, the entire thickness of which issufficiently small, and the resistance of the external terminal of whichis low.

[0040] In a lead frame of the present invention, the first conductorlayer comprises a gold layer.

[0041] According to the above constitution, it is possible to compose astable external terminal of low resistance, capable of easily forming analloy with solder.

[0042] In a lead frame of the present invention, the third conductorlayer comprises a gold layer.

[0043] According to the above constitution, it is possible to compose ahighly reliable external terminal, the connecting property with thesemiconductor chip of which is excellent.

[0044] In a lead frame of the present invention, the second conductorlayer comprises a metallic layer, the primary component of which isnickel.

[0045] According to the above constitution, it is possible to form alead of low resistance, the adhesion property to gold of which is high.

[0046] In this case, when the first conductor layer is made of stablemetal such as gold capable of easily forming an alloy together withsolder, a stable external terminal structure can be formed withoutconducting a plating process after the completion of sealing.

[0047] In this case, only the first conductor layer may be made ofstable material which is difficult to be oxidized, and the secondconductor layer may be made of inexpensive metal of low resistance. Thefirst and the third conductor layer may be made of material which can beeasily joined by solder. The third conductor layer may be made of thesame material as the material of the second conductor layer.

[0048] A method of manufacturing a lead frame of the present inventioncomprises: a step of forming a resist pattern on a surface of the leadframe body comprising a sheet-shaped body made of metal so that a leadforming region can be opened; a step of forming a groove portion forforming a lead of a predetermined depth in the lead forming region whenetching is conducted while the resist pattern is being used as a mask;and a step of forming a lead portion, the material of which is differentfrom the material of the lead frame body, so that the lead portion canprotrude from the groove portion onto a surface of the lead frame body.

[0049] According to the above constitution, it is possible to easilyform a highly accurate, reliable lead frame. Further, when the processof photolithography is used, it is possible to form a fine and highlyaccurate lead.

[0050] In a method of manufacturing a lead frame of the presentinvention, the step of forming the lead portion includes an electrolyticplating step of forming a metallic film on an inner wall of the grooveportion while the resist pattern is being used as a mask.

[0051] According to the above constitution, electrolytic plating can beconducted while the lead frame body is being used as an electrode.Therefore, a lead frame of low resistance can be easily formed in ashort period of time. Since electrolytic plating is conducted by usingthe resist pattern, which was used for forming the groove portion, as amask, the metallic film can be formed on an inner wall of the grooveportion. Due to the foregoing, it is possible to form an externalterminal having a layer structure in which the entire external terminalis covered with an outermost metallic film.

[0052] A method of manufacturing a lead frame of the present inventionfurther comprises a step of shrinking the resist pattern after thegroove portion is formed while the resist pattern is being used as amask so that a surface of the lead frame body round the groove portioncan be somewhat exposed.

[0053] According to the above structure, it is possible to expose acircumferential edge of the groove portion. Therefore, the conductorlayer can be formed in such a manner that the conductor layer rises fromthe inner wall of the groove portion to the flat portion.

[0054] A method of manufacturing a lead frame of the present invention,the step of forming the lead includes: a step of forming a firstconductor layer in the groove portion and in its periphery exposed fromthe resist pattern which has shrunk in the shrinking step; a step offorming a second conductor layer, which is laminated so that an end edgeof the first conductor layer can be left, on the first conductor layer;and a step of forming a third conductor layer on the second conductorlayer.

[0055] According to the above constitution, the first conductor layer isformed in such a manner that it rises from the inside of the grooveportion to the flat portion and then the second and the third layer arelaminated so that an end edge portion of the first conductor layer canbe left. Accordingly, an external terminal structure in which the entiresurface of the external terminal is covered with the first conductorlayer can be easily formed.

[0056] In a method of manufacturing a lead frame of the presentinvention, the step of forming the second conductor layer includes: astep of forming a thin conductive film on the first conductor layer; anda step of conducting etch-back on the thin conductive film by means ofanisotropic etching.

[0057] After the first conductor layer has been formed on the inner wallof the groove portion, the second conductor layer is formed and theprocess of etch-back is conducted. In this way, it is possible to form astructure in which the entire second conductor layer is covered with thefirst conductor layer.

[0058] In a method of manufacturing a lead frame of the presentinvention, the step of forming the lead includes a step of forming thefirst to the third conductor layer in the groove portion in order, andan interface of the first and the second conductor layer is locatedabove the surface of the lead frame body.

[0059] According to the above constitution, it is possible to form alead frame in which a semiconductor device surface exposed from thesealing resin used as an external terminal is covered with the firstconductor layer.

[0060] In a method of manufacturing a lead frame of the presentinvention, the step of forming the lead includes a step of forming abarrier layer for suppressing a reaction of the lead frame body and thefirst conductor layer, between the first conductor layer and the grooveportion.

[0061] According to the above method, the barrier layer can be easilyformed by a series of plating process. Therefore, manufacturing can beeasily performed.

[0062] In a method of manufacturing a lead frame of the presentinvention, the step of forming the groove portion includes ananisotropic etching step for forming a groove, the cross section ofwhich is a rectangle of 0.5 to 2.5 μm depth.

[0063] According to the above method, it is possible to form a finelead, the pattern accuracy of which is high. When the depth of therectangular groove is smaller than 0.5 μm, it is impossible tosufficiently reduce the resistance. When the depth of the rectangulargroove exceeds 2.5 μm, it become difficult to reduce the thickness ofthe semiconductor device.

[0064] A semiconductor device of the present invention comprises: asemiconductor chip; a lead portion connected to the semiconductor chip;and a piece of sealing resin, wherein a portion of the reverse face ofthe lead portion protrudes from a principal plane of the piece ofsealing resin, and the lead portion is a thin film formed from the outerface side to the inner face side.

[0065] According to the above constitution, an outer surface of the leadportion, which becomes an assembling face to be assembled to anassembling member such as a printed board, is arranged on the base sidein the process of film forming. Therefore, the surface can be maintainedin a state in which the orientation is excellent and the precision ishigh. Accordingly, it is possible to provide a highly reliableconnection.

[0066] In a semiconductor device of the present invention, the leadincludes: a first conductor layer; a second conductor layer laminatedinside the first conductor layer; and a third conductor layer formedinside the second conductor layer, wherein an entire surface of thelead, which is exposed from the sealing resin, is covered with the firstconductor layer.

[0067] According to the above constitution, the lead portion exposedfrom the sealing resin is only the first conductor layer. Therefore, itis possible to form a stable external terminal structure withoutconducting a plating process after the completion of sealing.

[0068] In a semiconductor device of the present invention, an interfaceof the first and the second conductor layer is located inside thesurface of the sealing resin.

[0069] According to the above constitution, after the completion ofassembling, the second conductor layer is perfectly sealed with thesealing resin, so that it can not be exposed onto the surface.Therefore, in the same manner as that of the aforementionedsemiconductor device, a stable lead frame of long life can be provided.

[0070] In a semiconductor device of the present invention, the firstconductor layer is made of metal capable of forming an alloy togetherwith solder.

[0071] In a semiconductor device of the present invention, the thirdconductor layer is made of metal which can be bonded by means ofwire-bonding.

[0072] In a semiconductor device of the present invention, the thirdconductor layer is made of metal which can be bonded to the bonding padsof the semiconductor chip.

[0073] In a semiconductor device of the present invention, the filmthickness of the first and the second conductor layer is 0.5 to 2 μm.

[0074] In a semiconductor device of the present invention, the firstconductor layer comprises a gold layer.

[0075] In a semiconductor device of the present invention, the thirdconductor layer comprises a gold layer.

[0076] In a semiconductor device of the present invention, the secondconductor layer comprises a metallic layer, the primary component ofwhich is nickel.

[0077] The present invention provides a method of manufacturing asemiconductor device, in which a lead frame is prepared, the lead frameincluding a lead frame body comprising a sheet-shaped body made of metaland also including a groove portion for forming a lead, the grooveportion being formed in a lead forming region on a surface of the leadframe body by a predetermined depth, and also including a lead portionformed so that the lead portion can protrude from the groove portiononto a surface of the lead frame body, the lead portion being made ofmaterial different from the lead frame body, the method of manufacturinga semiconductor device comprising: a semiconductor chip mounting step ofmounting a semiconductor chip on a lead frame and electricallyconnecting the semiconductor chip to the lead portion; a resin sealingstep of covering the semiconductor chip with the sealing resin; a stepof removing the lead frame body by means of etching; and a dicing stepof dicing into individual semiconductor devices.

[0078] According to the above constitution, in the case of mounting asemiconductor chip, the lead portion is fixed to the lead frame body.Therefore, a positional deviation is not caused and bonding can beperformed with high reliability. After the lead portion has beenpositively fixed by means of resin sealing, the lead frame body isremoved from the reverse side. Therefore, no deformation is caused inthe semiconductor device.

[0079] Since the lead portion is formed protruding from the grooveportion, the lead portion protruding from the sealing resin is notsubjected to a plating process after resin sealing, and a stableexternal terminal structure can be formed. Therefore, the semiconductordevice can be assembled to a printed board without the occurrence of animperfect contact.

[0080] A highly reliable thin semiconductor device can be easilyprovided.

[0081] After the completion of resin sealing, dicing is conducted sothat the semiconductor device can be divided into individual pieces.Since it is possible to make the lead portion not exist in the dicingregion, and it is unnecessary that a cutting blade cuts the lead portionat the time of dicing. Therefore, abrasion of the cutting blade can bereduced and the blade life can be extended.

[0082] In addition to that, the profile of the cross-section of the leadportion can be freely designed according to the profile of thecross-section of the groove portion. Therefore, a highly dense, accuratesemiconductor device can be easily formed.

[0083] In a method of manufacturing a semiconductor device of thepresent invention, the lead includes: a first conductor layer formed inthe groove portion; a second conductor layer laminated on the firstconductor layer; and a third conductor layer formed on the secondconductor layer, wherein the first conductor layer is assembled to anassembling member such as a printed board, and the third conductor layeris assembled to a bonding pad of the semiconductor chip.

[0084] According to the above constitution, a highly reliable thin typesemiconductor device can be easily provided at low cost.

[0085] In a method of manufacturing a semiconductor device of thepresent invention, the lead is formed so that it covers an entire innerwall of the groove portion.

[0086] According to the above constitution, a more highly reliable thintype semiconductor device can be formed without an increase in theman-day.

[0087] In a method of manufacturing a semiconductor device of thepresent invention, an interface of the first and the second conductorlayer is located above the surface of the lead frame body.

[0088] According to the above constitution, a highly reliable thin typesemiconductor device can be formed without an increase in the man-day.

[0089] In a method of manufacturing a semiconductor device of thepresent invention, the lead includes a barrier layer for suppressing areaction between the lead frame body and the first conductor layer, thebarrier layer being provided between the first conductor layer and thegroove portion, the method of manufacturing a semiconductor devicefurther comprising a step of removing the barrier layer by means ofetching after the completion of resin sealing.

[0090] According to the above constitution, it is possible to preventthe first conductor layer from deteriorating by an interface reactioncaused by heat generated in the bonding process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0091] In the accompanying drawings:

[0092]FIGS. 1A to 1D are views showing a semiconductor device of thefirst embodiment of the present invention, FIG. 1A an upper view, FIG.1B is a cross-sectional view taken on line A-A, FIG. 1C is a lower viewand FIG. 1D is a cross-sectional view taken on line B-B;

[0093]FIG. 2 is an enlarged cross-sectional view of a primary portion ofthe lead frame of the first embodiment of the present invention;

[0094]FIG. 3 is a conceptional schematic illustration of a semiconductordevice of the first embodiment of the present invention;

[0095]FIGS. 4A to 4C are process drawings of manufacturing a lead frameof the first embodiment of the present invention;

[0096]FIGS. 5A to 5D are process drawings of manufacturing a lead frameof the first embodiment of the present invention;

[0097]FIGS. 6A to 6C are process drawings of manufacturing asemiconductor device of the first embodiment of the present invention;

[0098]FIGS. 7A to 7C are process drawings of manufacturing asemiconductor device of the first embodiment of the present invention;

[0099]FIGS. 8A to 8D are process drawings of manufacturing a lead frameof the second embodiment of the present invention;

[0100]FIGS. 9A to 9D are process drawings of manufacturing a lead frameof the second embodiment of the present invention;

[0101]FIG. 10 is a view showing a semiconductor device formed in thesecond embodiment of the present invention; and

[0102]FIGS. 11A to 11C is a view showing a conventional semiconductordevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0103] Next, embodiments of the present invention will be explained indetail referring to the drawings.

First Embodiment

[0104]FIGS. 1A to 1C are respectively an upper view, a cross-sectionalview taken on line A-A, a lower view and a cross-sectional view taken online B-B showing a semiconductor device of the first embodiment of thepresent invention. As shown in the drawings, this semiconductor deviceis a face assembly type semiconductor device, which is formed asfollows. The semiconductor chip 11 composing a bipolar transistor is seton the die pad 10 a, and the pad connected to the collector and the padconnected to the emitter are respectively electrically connected to thelead terminals 10 b, 10 c via the bonding wires 12 and sealed withresin. From the reverse face of this sealing resin, the die pad 10 acomposing the base terminal and the lead terminals 10 b, 10 c composingthe emitter terminal and the collector terminal are somewhat protruded,so that a face assembly type semiconductor device can be formed.

[0105] The die pad and the lead terminal comprise a three layerstructure. As shown in FIG. 2 which is an enlarged view of the primaryportion, the die pad and the lead terminal include: a barrier layer 3 acomprising a nickel layer, the film thickness of which is 0.0005 mm; afirst conductor layer 3 b comprising a gold layer, the film thickness ofwhich is 0.0015 mm, formed on this barrier layer 3 a; a second conductorlayer 3 c comprising a nickel layer, the film thickness of which is0.030 mm, laminated on the first conductor layer; and a third conductorlayer 3 d comprising a gold layer, the film thickness of which is 0.0007mm, formed on the second conductor layer.

[0106] As shown in FIG. 3 which is an enlarged view of the primaryportion, the characteristics of this layer structure are described asfollows. In the groove portion 2 of 0.008 mm thickness formed on thesurface of a copper plate which is the main body 1 of the lead frame,the barrier layer 3 a, the first conductor layer 3 b, the secondconductor layer 3 c and the third conductor layer 3 d are successivelylaminated in order, and the first conductor layer is formed so that itcovers an inner wall of the groove portion 2 via the barrier layer 3 a.This view shows a state before resist R is removed.

[0107] Next, a method of assembling this semiconductor device will beexplained below.

[0108] First, a method of manufacturing this lead frame will beexplained.

[0109] According to this method, the shallow groove portion 2 is formedon a surface of the lead frame body, which comprises a plate-shaped body(copper plate) made of metal, by means of photolithography. Then, thelead portion comprising a metallic layer of the four-layer structure isformed in this groove portion 2 by means of electrolytic plating so thatthe lead portion can protrude from the groove onto the surface of thelead frame body.

[0110] As shown in FIG. 4A, the lead frame body 1 comprising a copperplate is prepared.

[0111] As shown in FIG. 4B, resist R is coated.

[0112] After that, as shown in FIG. 4C, patterning is conducted onresist R by means of photolithography. While this resist R is being usedas a mask, anisotropic etching is conducted so as to form the shallowgroove 2 of 0.5 to 2.5 μm thickness, the cross-section of which isrectangular.

[0113] After that, as shown in FIG. 5A, while resist R is being left asit is, the lead frame body 1 is dipped in a plating solution which is awater solution of nickel sulfonate, and the nickel layer 3 a, which is abarrier layer, is formed by means of electrolytic plating.

[0114] Then, as shown in FIG. 5B, a gold layer, which is the firstconductor layer 3 b, and a nickel layer, which is the second conductorlayer 3 c, are successively laminated by means of electrolytic plating.At this time, a nickel layer, which is the barrier layer 3 a, and a goldlayer, which is the first conductor layer 3 b, are formed on the entireinner wall of the groove portion 2.

[0115] Further, a gold layer, which is the third conductor layer 3 d, isformed.

[0116] Finally, as shown in FIG. 5D, resist R is removed, and the leadframe of the first embodiment of the present invention is formed.

[0117] Next, explanations will be made into a method of manufacturing abipolar transistor in which this lead frame is used.

[0118] First, as shown in FIG. 6A, a reverse face of the semiconductorchip 11 is mounted on and fixed to the die pad 10 a of the lead frameshown in FIGS. 4A to 5D. Then, the semiconductor chip and the leadterminal are electrically connected to each other by the bonding wire12.

[0119] After that, as shown in FIG. 6B, resin sealing is conducted withepoxy resin. In this way, the semiconductor device fixed by the sealingresin 13 is formed.

[0120] Finally, as shown in FIG. 6C, the lead frame body 1 comprising acopper plate is removed by means of etching. In this way, thesemiconductor device, the barrier layer 3 a and the first conductorlayer 3 b of which are exposed from the sealing resin 13, can beobtained.

[0121] Then, the adhesive tape 14 is stuck onto an exposed side of thelead terminal 3 (3 a, 3 b, 3 c) as shown in FIG. 7A.

[0122] After that, as shown in FIG. 7B, the dicing groove 15 is formedby means of cutting from one side, on which the adhesive tape 14 is notstuck, to the other side, on which the adhesive tape 14 is stuck, withthe dicing blade 16, so that the semiconductor device ca be separated.

[0123] As shown in FIG. 7C, when the semiconductor device is assembledto a printed board, the semiconductor device is separated from thisadhesive tape 14 and assembled.

[0124] In this connection, after the completion of bonding, the barrierlayer may be removed by etching together with the lead frame body afterresin sealing has been completed.

[0125] According to the above structure, since the lead portionprotrudes from the sealing resin surface, assembling can be stablyperformed so that the lead portion can protrude from the sealing resin.Accordingly, it is possible to provide a semiconductor device having noimperfect contact in the case of assembling the semiconductor deviceonto a printed board. As described above, according to the embodiment ofthe present invention, it is possible to compose a stable externalterminal structure without conducting a plating process after thecompletion of resin sealing.

[0126] The semiconductor chip is mounted on the lead portion, and anelectrical connection is conducted by means of wire bonding or directbonding. Then, resin sealing is conducted and the lead frame body isremoved by etching from the reverse face. Due to the foregoing, a thintype highly reliable semiconductor device can be provided. Therefore,the thickness of the semiconductor device can be reduced as small aspossible. That is, the thickness of the semiconductor device can bereduced to about three fourths of the thickness of the conventionalsemiconductor device.

[0127] In the case of mounting the semiconductor chip, since the leadportion is fixed to the lead frame body, no positional shift is causedand bonding can be positively conducted with high reliability. After thesemiconductor chip has been positively fixed by means of resin sealing,the lead frame body is removed from the reverse face. Therefore, nodeformation is caused in the semiconductor device. Since the barrierlayer is provided, even when the connecting portion is heated to a hightemperature at the time of mounting the semiconductor element or wirebonding, the lead portion can be prevented from deteriorating. Thisbarrier layer may be left as it is. Alternatively, this barrier layermay be finally removed by etching. In the case of etching, when etchingis conducted after the completion of resin sealing, since the otherportions are covered with the sealing resin, it may be dipped in theetching solution as it is. Therefore, the working property is veryexcellent.

[0128] After the completion of resin sealing, the semiconductor deviceis diced into individual semiconductor devices so that the semiconductordevice can be divided into individual pieces. At this time, since nolead portion exists in the dicing region, it is unnecessary for theblade to cut the lead portion at the time of dicing. Therefore, abrasionis seldom caused in the blade, and life of the blade can be extended.

[0129] Since the lead portion is guided out only from the principalplane of the semiconductor device, no air gets into the semiconductordevice from the portion where the lead portion is guided out. Therefore,it is possible to provide a highly reliable semiconductor device.

[0130] Further, the cross-sectional profile of the lead portion can befreely designed according to the cross-sectional profile of the grooveportion. Accordingly, it is possible to form a highly accurate andhighly dense lead portion pattern.

[0131] Since the lead portion exposed from the sealing resin of thesemiconductor device comprises a gold layer, a stable external terminalstructure can be formed without conducting a plating process after thecompletion of resin sealing.

[0132] In this connection, the first conductor layer may be made ofmetal such as gold, tin and palladium capable of forming an alloytogether with solder.

[0133] Since the barrier layer is existing, it is possible to preventthe first conductor layer and the lead frame body from deteriorating byan interface reaction caused by heat generated in the bonding process.This barrier layer may be made of nickel, titanium or tungsten. Thebarrier layer may be formed thin. Alternatively, the barrier layer maybe finally removed by etching. In the case of eutectic solder ofgold-silicon, it is necessary to conduct bonding at a high temperatureof about 400° C. On the other hand, in the case of eutectic solder suchas gold-tin or gold-germanium, which can be bonded at a relatively lowtemperature of about 350° C., it is unnecessary to provide the barrierlayer.

[0134] In the lead frame of the present invention, when the firstconductor layer is made of metal such as gold which can easily form analloy with solder, bonding can be excellently conducted when thesemiconductor device is assembled to a printer board.

[0135] When the third conductor layer is made of metal, the wire bondingproperty of which is high, the semiconductor chip can be easilyassembled.

[0136] This lead frame can be applied to both wire bonding and directbonding. The third conductor layer may be made of metal, the bondingproperty with the bonding pad of the semiconductor chip of which ishigh.

[0137] The first and the third conductor layer are provided forenhancing the bonding property and the assembling property. Therefore,it is preferable that the first and the third conductor layer are formedto be sufficiently thin.

[0138] Due to the foregoing, the entire thickness can be sufficientlyreduced and further the film thickness of the second conductor layer canbe made to be sufficiently thick. Accordingly, it is possible to composea semiconductor device, the entire thickness of which is sufficientlysmall, having an external terminal of low resistance.

[0139] In this connection, in the first embodiment described above, thebarrier layer is provided. However, it is possible to adopt a structurein which no barrier layer is provided and the lead portion comprises athree-layer structure.

[0140] According to the method of manufacturing a lead frame of thisembodiment, it is possible to form a highly accurate and reliable leadframe through the process of photolithography.

[0141] Since the first conductor layer is formed on the entire innerwall of the groove portion of the lead frame body via the barrier layer,the second conductor layer is not exposed from the sealing resin afterthe completion of resin sealing. As shown in the Second Embodimentdescribed hereinafter, it is preferable that an interface of the firstand the second conductor layers is located above the upper face of thegroove portion. In other words, it is preferable that the interface ofthe first and the second conductor layers is located above the upperface of the lead frame body. However, even when the interface of thefirst and the second conductor layer is located on a lower layer of theupper face of the groove portion, no problems are caused if the secondlayer is made of material which is difficult to be oxidized.

[0142] According to the method of manufacturing a lead frame of thepresent invention, in the process of forming the lead portion, ametallic film is formed on the inner wall of the groove portion whilethe resist pattern is being used as a mask. Therefore, the lead of lowresistance can be easily formed in a short period of time.

[0143] Since etching is conducted while the resist pattern used forforming the groove portion is being used as a mask, it is possible toform a conductive film such as a metallic film along the inner wall ofthe groove portion. Therefore, an external terminal can be easilyformed, the layer structure of which is formed in such a manner that theentire device is covered with the outermost conductive film.

Second Embodiment

[0144] Next, the second embodiment of the present invention will beexplained below.

[0145] In the semiconductor device of this embodiment, the externalterminal structure is formed as follows. As show in FIG. 10, after thefirst conductor layers 3 c, 3 d have been formed in such a manner thatthe first conductor layers 3 c, 3 d rise from the inside of the grooveportion to the flat portion, the second and the third conductor layerare laminated on each other so that an end edge portion of the firstconductor layer 3 b can be left, and the entire surface of the externalterminal composes the external terminal structure covered with the firstconductor layer.

[0146] In this case, there is provided a nickel layer, which is used asthe barrier layer 3 a, on the outer layer of the first conductor layer 3b.

[0147] As described above, the conductor layer is formed in such amanner that the circumferential edge of the groove portion is exposedand made to rise from the inner wall of the groove portion to the flatportion. Accordingly, in this constitution, the entire surface of thelead terminal is covered with the first conductor layer, and the secondconductor layer 3 c comprising a nickel layer is embedded in the resin,so that the second conductor layer 3 c is not exposed to the outsideair.

[0148] In the method of manufacturing the lead frame used for thesemiconductor device, when the lead portion is formed, an electrolyticplating process is used in which a metallic film is formed on the innerwall of the groove portion while the resist pattern is being used as amask.

[0149] According to this method, electrolytic plating is conducted whilethe resist pattern used for forming the groove portion is being used asa mask. Therefore, it is possible to form a conductive film such as ametallic film on the inner wall of the groove portion, and an externalterminal having a layer structure, in which the entire device is coveredwith the outermost conductive film, is formed.

[0150]FIGS. 8 and 9 are views showing a lead frame of the secondembodiment of the present invention, and FIG. 10 is a view showing asemiconductor device comprising this lead frame.

[0151] This method comprises a step of shrinking a resist pattern aftera groove portion is formed while the resist pattern is being used as amask so that a surface of the lead frame body round the groove portioncan be somewhat exposed.

[0152] As shown in FIGS. 8A to 8C, the manufacturing process from thebeginning to the formation of the groove portion 2 is the same as themanufacturing process explained in the first embodiment referring toFIGS. 4A to 4C. As shown in FIG. 8D, after heated at 500° C. for 30minutes, resist pattern R is shrunk so that resist pattern R_(s) isformed, and the peripheral portion of the groove portion 2 is exposed.

[0153] After that, as shown in FIG. 9A, while resist pattern R_(s) isbeing left as it is, the device is dipped in a plating solutioncontaining a nickel sulfonate water solution, and the nickel layer 3 a,which is the barrier layer 3 a, is formed by means of electrolyticplating. At this time, the barrier layer 3 a is formed so that it canreach the flat portion in the periphery of the groove portion 2 alongthe inner wall of the groove portion 2.

[0154] Next, as shown in FIG. 9B, a gold layer, which is the firstconductor layer 3 b, is successively formed, and the first conductorlayer in the flat portion is removed by means of anisotropic etching.

[0155] Further, as shown in FIG. 9C, a nickel layer, which is the secondconductor layer 3 c, is successively laminated on the first conductorlayer 3 b by means of electrolytic plating.

[0156] Further, a gold layer, which is the third conductor layer 3 d, isformed.

[0157] Finally, as shown in FIG. 9D, resist pattern R_(s) is removed. Inthis way, a lead frame of the second embodiment of the present inventionis formed.

[0158] Assembling of the lead frame of the semiconductor device of thesecond embodiment is conducted in the same manner as that of the firstembodiment.

[0159] As shown in FIG. 10, in the thus formed semiconductor device, theentire surface is covered with the first conductor layer comprising thegold layer. Therefore, the second conductor layer made of nickel is notexposed to the surface. Accordingly, it is possible to form a stablesemiconductor device in which no surface is oxidized and the life islong.

[0160] Since the barrier layer 3 a is provided, even when wire bondingis conducted on the third conductor layer by solder of hightemperatures, there is no possibility that the first conductor layerreacts with the lead frame body.

[0161] In the above embodiment, explanations are made into the assemblyof a bipolar transistor. However, it should be noted that the presentinvention is not limited to the above discrete element. Of course, thepresent invention can be applied to IC and LSI.

[0162] As explained above, according to the lead frame of the presentinvention, it is possible to form a highly accurate, reliable, thin typesemiconductor device.

[0163] According to the method of manufacturing a lead frame of thepresent invention, since a portion of the metallic substrate isselectively, lightly etched and a lead terminal is formed in this grooveportion, a thin type semiconductor device can be very easily formed.

[0164] According to the present invention, it is possible to provide ahighly reliable thin type semiconductor device.

[0165] According to the method of manufacturing a semiconductor deviceof the present invention, no positional shift is caused and a highlyreliable thin type semiconductor device can be assembled at a highyield.

[0166] The present invention is not limited to the embodiments and thedescription thereof at all. If various changes which can be easilyconceived by those skilled in the art are not departed from thedescription of the scope of claim, they may be contained in the presentinvention.

What is claimed is:
 1. A lead frame comprising: a lead frame bodycomprising a sheet-shaped body made of metal; a groove portion forforming a lead which is formed by a predetermined depth in a leadforming region on a surface of the lead frame body; and a lead formed sothat the lead can protrude from the groove portion onto the surface ofthe lead frame body, the lead being made of material different frommaterial of the lead frame body.
 2. A lead frame according to claim 1,the lead including: a first conductor layer formed in the grooveportion; a second conductor layer formed on the first conductor layer;and a third conductor layer formed on the second conductor layer,wherein the first conductor layer is assembled to an assembling member,and the third conductor layer is assembled to a bonding pad of asemiconductor chip.
 3. A lead frame according to claim 2, wherein thefirst conductor layer covers an entire inner wall of the groove portion.4. A lead frame according to claim 2, wherein an interface of the firstand the second conductor layer is located above the surface of the leadframe body.
 5. A lead frame according to claim 1, wherein the leadincludes a barrier layer for suppressing a reaction between the leadframe body and the first conductor layer, the barrier layer beingprovided between the first conductor layer and the groove portion.
 6. Alead frame according to claim 2, wherein the first conductor layer ismade of metal capable of forming an alloy together with solder.
 7. Alead frame according to claim 2, wherein the film thickness of the firstand the second conductor layer is 0.5 to 2 μm.
 8. A lead frame accordingto claim 2, wherein the first conductor layer comprises a gold layer. 9.A lead frame according to claim 2, wherein the third conductor layercomprises a gold layer.
 10. A lead frame according to claim 2, whereinthe second conductor layer comprises a metallic layer, the primarycomponent of which is nickel.
 11. A method of manufacturing a lead framecomprising: a step of forming a resist pattern on a surface of the leadframe body comprising a sheet-shaped body made of metal so that a leadforming region can be opened; a step of forming a groove portion forforming a lead of a predetermined depth in the lead forming region whenetching is conducted while the resist pattern is being used as a mask;and a step of forming a lead, the material of which is different fromthe material of the lead frame body, so that the lead can protrude fromthe groove portion onto a surface of the lead frame body.
 12. A methodof manufacturing a lead frame according to claim 11, wherein the step offorming the lead includes an electrolytic plating step of forming ametallic film on an inner wall of the groove portion while the resistpattern is being used as a mask.
 13. A method of manufacturing a leadframe according to claim 11, further comprising a step of shrinking theresist pattern after the groove portion is formed while the resistpattern is being used as a mask so that a surface of the lead frame bodyround the groove portion can be somewhat exposed.
 14. A method ofmanufacturing a lead frame according to claim 11, the step of formingthe lead including: a step of forming a first conductor layer in thegroove portion and in its periphery exposed from the resist patternwhich has shrunk in the shrinking step; a step of forming a secondconductor layer, which is laminated so that an end edge of the firstconductor layer can be left, on the first conductor layer; and a step offorming a third conductor layer on the second conductor layer.
 15. Amethod of manufacturing a lead frame according to claim 14, the step offorming the second conductor layer including: a step of forming a thinconductive film on the first conductor layer; and a step of conductingetch-back on the thin conductive film by means of anisotropic etching.16. A method of manufacturing a lead frame according to claim 11,wherein the step of forming the lead includes a step of forming thefirst to the third conductor layer in the groove portion in order, andan interface of the first and the second conductor layer is locatedabove the surface of the lead frame body.
 17. A method of manufacturinga lead frame according to claim 11, wherein the step of forming the leadincludes a step of forming a barrier layer for suppressing a reaction ofthe lead frame body and the first conductor layer, between the firstconductor layer and the groove portion.
 18. A method of manufacturing alead frame according to claim 11, wherein the step of forming the grooveportion includes an anisotropic etching step for forming a groove, thecross section of which is a rectangle of 0.5 to 2.5 μm depth.
 19. Asemiconductor device comprising: a semiconductor chip; a lead connectedto the semiconductor chip; and a piece of sealing resin, wherein aportion of the reverse face of the lead protrudes from a principal planeof the piece of sealing resin, and the lead is a thin film formed fromthe outer face side to the inner face side.
 20. A semiconductor deviceaccording to claim 19, the lead including: a first conductor layer; asecond conductor layer laminated inside the first conductor layer; and athird conductor layer formed inside the second conductor layer, whereinan entire surface of the lead, which is exposed from the sealing resin,is covered with the first conductor layer.
 21. A semiconductor deviceaccording to claim 20, wherein an interface of the first and the secondconductor layer is located inside the surface of the sealing resin. 22.A semiconductor device according to claim 19, wherein the firstconductor layer is made of metal capable of forming an alloy togetherwith solder.
 23. A semiconductor device according to claim 19, whereinthe film thickness of the first and the second conductor layer is 0.5 to2 μm.
 24. A semiconductor device according to claim 20, wherein thefirst conductor layer comprises a gold layer.
 25. A semiconductor deviceaccording to claim 20, wherein the third conductor layer comprises agold layer.
 26. A semiconductor device according to claim 20, whereinthe second conductor layer comprises a metallic layer, the primarycomponent of which is nickel.
 27. A method of manufacturing asemiconductor device, in which a lead frame is prepared, the lead frameincluding a lead frame body comprising a sheet-shaped body made of metaland also including a groove portion for forming a lead, the grooveportion being formed in a lead forming region on a surface of the leadframe body by a predetermined depth, and also including a lead formed sothat the lead can protrude from the groove portion onto a surface of thelead frame body, the lead being made of material different from the leadframe body, the method of manufacturing a semiconductor devicecomprising: a semiconductor chip mounting step of mounting asemiconductor chip on a lead frame and electrically connecting thesemiconductor chip to the lead; a resin sealing step of covering thesemiconductor chip with the sealing resin; a step of removing the leadframe body by means of etching; and a dicing step of dicing intoindividual semiconductor devices.
 28. A method of manufacturing asemiconductor device according to claim 27, the lead including: a firstconductor layer formed in the groove portion; a second conductor layerlaminated on the first conductor layer; and a third conductor layerformed on the second conductor layer, wherein the first conductor layeris assembled to an assembling member, and the third conductor layer isassembled to a bonding pad of the semiconductor chip.
 29. A method ofmanufacturing a semiconductor device according to claim 28, wherein thefirst conductor layer is formed so that it covers an entire inner wallof the groove portion.
 30. A method of manufacturing a semiconductordevice according to claim 28, wherein an interface of the first and thesecond conductor layer is located above the surface of the lead framebody.
 31. A method of manufacturing a semiconductor device according toclaim 28, wherein the lead includes a barrier layer for suppressing areaction between the lead frame body and the first conductor layer, thebarrier layer being provided between the first conductor layer and thegroove portion, the method of manufacturing a semiconductor devicefurther comprising a step of removing the barrier layer by means ofetching after the completion of resin sealing.